#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main()
{
	double x1, x2, x3, y1, y2, y3;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	//海伦公式
	double a = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)),
	      b = sqrt((x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3)),
	      c = sqrt((x3 - x2) * (x3 - x2) + (y3 - y2) * (y3 - y2));
	double p = (a + b + c) / 2;
	cout << fixed << setprecision(2) << sqrt(p * (p - a) * (p - b) * (p - c));
	return 0;
}
